I made spc control but something is wrong, I get only clean signal when pot is all the way up, exactly the same as bypassed.I used substitute opamp - tl072 and ne5532, I found it can be substituted with those, could this be problem?

I made spc control but something is wrong, I get only clean signal when pot is all the way up, exactly the same as bypassed.I used substitute opamp - tl072 and ne5532, I found it can be substituted with those, could this be problem?

Does your build affect the sound at other points in the pot rotation or does it always sound like it is bypassed no matter the position of the pot? These circuits are designed so that when they are turned down to minimum, the signal sounds the same as bypassed (because there is no on/off switch for them when used in a guitar). You may have your wires to the pot backwards if turning clockwise decreases the affected signal.

I made spc control but something is wrong, I get only clean signal when pot is all the way up, exactly the same as bypassed.I used substitute opamp - tl072 and ne5532, I found it can be substituted with those, could this be problem?

Does your build affect the sound at other points in the pot rotation or does it always sound like it is bypassed no matter the position of the pot? These circuits are designed so that when they are turned down to minimum, the signal sounds the same as bypassed (because there is no on/off switch for them when used in a guitar). You may have your wires to the pot backwards if turning clockwise decreases the affected signal.

It is possible I wired it backwards, but when turned it cuts volume, there is no any boost.

rockstrana wrote:It is possible I wired it backwards, but when turned it cuts volume, there is no any boost.

Its been a while since I have heard one these things, but I'm pretty sure there is supposed to be at least a slight boost... :S If you have some nice close up pics of your wiring I would post them to the troubleshooting section and see if someone can help you out.

My 10 year old SPC has a peak around 600Hz, so let's forget the statement about that 1.3kHz peak. I read that on the website of the german seller thomann.de, and it's most probably wrong.

But the picture of the SPC shows two more parts, that are not in the schematic: A capacitor and a diode or transistor, both close to the power supply wire. What are these for? Filtering or polarity protection?

roseblood11 wrote:But the picture of the SPC shows two more parts, that are not in the schematic: A capacitor and a diode or transistor, both close to the power supply wire. What are these for? Filtering or polarity protection?

They are present on the schematic - upper right corner. You're right - their purpose is filtering and polarity protection. Look at the bajaman's PCB, they are the same as EMG's. There's one difference - 1k resistor is missing.

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Vero layout, small changes to the circuit for use with pasie pickups. I used a OPA2134, because the higher current draw doesn't matter for me, as I will add a true bypass pushbutton switch for the mid boost. Could be replaced with LF442, TL062, TLC2272 ...

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Is the circuit still the same in this version?https://www.youtube.com/watch?v=eJG25PEsyLYHe puts the EXG before the SPC in the signal chain - with the input resistors shown on the schematics in this thread, this wouldn`t work with passive pickups...